With the development of the world economy, the price of the international oil fluctuates violently in recent years, and the oil resource is anticipated to decrease in the future, so oil has already become a bottle neck of the development of the world economy, and making use of new energy sources has become a new trend in the development of economy. With the growing shortage of the global fossil energy and the increasing pollution of the environment, the demand for clean and renewable energy sources is growing more and more imperative.
As carriers of high efficient renewable energy sources, lithium ion batteries are widely used in electron and communication industry, especially in personal communication tools such as mobile phones, PDA and so on. Color screen technology, multimedia message technology, Bluetooth technology and photographing technique have been introduced one after another in recent two years with the rapid development of communication technology, which puts forward higher standard for the capacity, volume, weight, electrochemical performance and safety performance of lithium ion battery. The working voltage of a single lithium ion battery is usually ranged from 2.4 v to 4.5 v. What's more, the capacity of a single battery is limited.
The safety performance of the lithium ion battery is more important for the electric vehicles, UPS, communication equipments and so on in the application fields, of which large capacity and large power are needed. At present, the power battery with large capacity and large power is assembled by connecting single cells in series and/or in parallel. The key factor which affects the safety performance of the lithium ion battery is that the heat of the battery produced in the working process can't be released in time. Instead, the heat is accumulated gradually and becomes out of control to cause an explosion at last, which will bring harm and damages to the users. Now the lithium ion battery is solid, which is not good for eliminating heat. So for the people in this field, it has become one of the highlights of research whether the structure of a single lithium ion battery is beneficial to heat radiation and meets the requirements of unconformity of the battery or not.
The most common power batteries in the prior art are solid and in shape of circle or square. These two kinds of batteries have the same defects of low safety performance, less charge/discharge cycles and bad operational performances as follows:
The interior of the square battery is assembled by a number of electrode plates. In working process, the inner ions of the battery move at high speed and the temperature inside the battery rises. Due to the whole structure defects of the square battery, the square battery stops the internal heat from being released, so that the outer case of the power battery and the inner electrode plates distort, and the spaces between the inner electrode plates of the battery become unequal, which will affect the charging characteristics and discharging characteristics. What's more, that the internal heat can't be released will result in the instable performance, explosion and short service life of the battery.
The interior of the circular battery is assembled by rolling a number of electrode plates. In working process, the inner ions of the battery move at high speed and the temperature inside the battery rises. Due to the whole structure defects of the circular battery, the circular battery stops the internal heat from being released, so that the spaces between the inner electrode plates of the battery become unequal, which will affect the charging characteristics and discharging characteristics. What's more, that the internal heat can't be released will result in the instable performance, explosion and short service life of the battery.
Now it has become a common sense of governments of all countries and groups of enterprises to develop power batteries with large capacity, long service life and good safety performance. It is anticipated that this kind of power battery will be one of the most important power energy resources of electric vehicles in the 21st century and will be widely used in man-made satellites, aeronautics and space industry, and energy storage.